WATCHING PAINT DRY: TOXICITY AND XRF DETECTION OF COPPER IN SEDIMENT CONTAMINATED BY DRYDOCK MAINTENANCE

Abstract

Antifouling hull coatings prolong the service lives of vessels and increase fuel efficiency by protecting against biofouling organisms. One of the most effective types of antifouling coating is biocide-infused epoxy. Organotin coatings, a popular and effective class of biocidal coating, were largely banned in the 2000s in recognition of their severe environmental impact and replaced with paints using copper or zinc as their primary biocides. Coating maintenance in shipyards can still release material such as paint fragments into the environment, which could contribute to the presence of microplastic (MP) paint particles in sediment near shipyards. These paint particles, like other microplastics, are often classed by size and polymer type, but in all plastic wastes manufacturing additives are often more environmentally consequential than the polymers that make up the bulk of the material. This study investigated whether it was possible to use portable X-Ray Fluorescence Spectrometry (XRF) to assess the presence of copper-based biocidal Antifouling Paint Particles (APP) in the sediments near active shipyards and whether toxicity of these sediments was correlated with copper content when compared to sediment spiked with copper products in the lab. Toxicity was evaluated using 10-day acute toxicity test procedures for the amphipod Leptocheirus plumulosus modified for reduced volume. We hypothesized that sediment toxicity would be predicted by XRF-reported copper content. We tested spiked sediment series of increasingly complex and environmentally representative matrices for toxicity, beginning with pure copper compounds, proceeding to new and used antifouling paints and then used abrasive blast media contaminated with these coatings collected from active shipyards. Finally, we performed toxicity tests and XRF analysis of field-collected sediments from three urban rivers (Cuyahoga River, OH, USA; Curtis Creek, MD, USA; and Elizabeth River, VA, USA). Geographic differences in copper concentrations relative to location of the nearest shipyard(s) and number of yards were considered. Ultimately, this research will lay the groundwork for further classification of understudied MPs in the marine environment and provide a starting point for further assessment of sediments near shipyards.